In recent years, miniaturization of design rule has progressed, and signal transmission delay has governed the limit of high-speed processing. Thus, the conductive wiring material has been converted from aluminum to copper having lower electric resistance, and the interlayer dielectric film has been converted from a silicon oxide film to a low dielectric constant film (a film having a specific dielectric constant of less than 3). As a method of decreasing the dielectric constant of an interlayer dielectric film, there has been known a method of introducing a fluorine atom or a carbon atom having a small atomic radius into the interlayer dielectric film. In particular, as an interlayer dielectric film, the dielectric constant of which has been decreased by introducing a carbon atom into a silicon oxide film, carbon-incorporated silicon oxide (SiOC) has been widely used.
In a step of cleaning a semiconductor device, when the semiconductor device is washed by repeatedly using a cleaning solution according to single-wafer cleaning, there is a case where a silicon wafer serving as a dummy (hereinafter referred to as a “test wafer”) is cleaned in the intervals of the cleaning of a semiconductor device of interest. This cleaning is carried out to examine whether or not an unacceptable change is generated in the properties of the cleaning solution due to the repeated use of the cleaning solution. When SiOC is used as a material for the semiconductor device as a cleaning target, there is a case where a test wafer prepared by forming a SiOC film particularly on a single crystal silicon wafer is used.
Such a test wafer prepared by forming a SiOC film on a silicon wafer is repeatedly used. However, the number of using the test wafer is limited due to corrosion caused by a cleaning solution. With regard to such a test wafer, which is hardly used due to repeated use, it is desired to recycle the test wafer by removing the SiOC film from it and then forming a SiOC film again on it. Herein, in the step of removing the SiOC film from the test water, it is necessary to promptly remove the SiOC film from the test wafer. Accordingly, it has been strongly desired to develop a cleaning solution, which removes the SiOC film from the wafer in a short time and does not corrode Si.
Patent Literature 1 (International Publication WO 2009/031270) describes that a recycled silicon wafer having a thickness of 600 μm or more can be used as a dummy wafer.
Patent Literature 2 (JP Patent Publication (Kokai) No. 10-177998 A (1998)) proposes a cleaning solution comprising hydrofluoric acid and ammonium fluoride, and having a pH value of 1.8 to 6. However, since this cleaning solution cannot remove SiOC from a wafer at a satisfactory level, it cannot be used in industrial production activities (see Comparative Examples 9 and 10).
Patent Literature 3 (International Publication WO 2004/019134) proposes a cleaning solution comprising at least one selected from the group consisting of organic acids and organic solvents, and hydrofluoric acid. However, since this cleaning solution cannot remove SiOC from a wafer, it cannot be used in industrial production activities (see Comparative Example 11).
Patent Literature 4 (JP Patent Publication (Kokai) No. 2006-203181 A) proposes a cleaning solution comprising hydrofluoric acid and nitric acid, and further comprising at least one of ammonium fluoride and ammonium chloride. However, since this cleaning solution cannot remove SiOC from a wafer, it cannot be used for the purpose of recycling a test wafer, in which a SiOC film has been formed on a silicon wafer (see Comparative Examples 12 and 13).